During manufacture of pneumatic tires a fiber-reinforced, rubberized elongated strip is cut into segments of a predetermined length at predetermined intervals at a predetermined bias angle throughout the length of the strip. The sheet segments thus produced are then joined to one another with a front marginal portion of one segment lapped onto a rear marginal portion of another until the segments form an elongated strip, or fabric ply. A known example of a sheet joining apparatus used for the production of such a fabric ply is shown in Japanese Provisional Patent Publication No. 53-2573. The sheet joining apparatus disclosed therein however is composed of a disproportionately large number of component units and members involving extremely intricate motions and requiring various laborious adjustments. The prior-art sheet joining apparatus thus requires much time and labor for the adjustment of such members and units and is for this reason not operable for the manufacture of fabric plies with an acceptable degree of production efficiency. The present invention contemplates resolution of such a problem encountered in a prior-art sheet joining apparatus. It is accordingly a prime object of the present invention to provide a sheet joining apparatus which is simple in construction and capable of providing an increased production efficiency.